Ventilation is required in panels used for making boxes, drums, cans, containers, cases, pallets, crates, shipping containers etc. Many of these applications are used for storage purposes where, commonly, ventilation or insulation or both are important considerations. Both of these considerations are important in designing fast food packaging.
Fast food packaging has three aims. The packaging, such as, a carton or other sort of box, should retain the heat of the food it contains, it should prevent the food from becoming soggy as the result of steam condensing into water on the inner surface of the carton, and also should be cost effective, as the packaging is usually disposable.
Generally, packaging that is widely used at present achieves the last aim with only one of the first two aims. It has been difficult to create packaging, which meets all three objectives simultaneously.
Known packaging fails to meet all of these three aims partly because of the following reasons. As the packaging, and the food within it, are transported, heat from the food and packaging disperses and steam is released into the atmosphere within the packaging. The packaging is cooler than the food. As the heated steam from the food rises vertically above the food, it rises towards the lid, or covering, of the packaging. On contact with the lid, the steam condenses into water on the lid transferring heat to the packaging. The condensed water is then free to fall back on to the food making it soggy and reducing its taste.
Cartons made of Styrofoam attempt to overcome this problem by retaining the heat within the carton, as Styrofoam is a highly insulative material. However, after time, heat still escapes from the carton, so that condensation forms within the carton above the food.
Another carton that is well known is made of corrugated paperboard. Corrugated paperboard is used to make the carton because of properties inherent in its corrugated structure. The inherent corrugated structure imparts resistance to, and distribution of, forces applied parallel to and perpendicular to the corrugations of the corrugated structure. When a force is applied in the direction of the flutes in the corrugated structure, the flutes are in compression, and, acting like columns, thereby resist the compression force. The corrugated structure therefore improves the compression strength of the board. When the force is applied perpendicular to the direction of the flutes of the corrugated structure, the flutes deform, absorbing the energy of the impacting force and distributing the force through the board. Thus, the corrugated structure improves the strength of the board by providing resistance to the applied force.
Where multilayer corrugated board is used, the layers of the board are generally used with their flutes parallel to the flutes of the adjacent layers. Thus, in a multilayer board it is possible to withstand compressive forces and forces that would normally deform the flutes. In these circumstances, the board remains rigid. The food within a carton made of paperboard, typically of three or five ply, is protected from physical impacts during transportation. Yet, even with these advantages, condensation would form on the surfaces on the inside of this carton, making the food soggy on delivery.
Therefore, as these types of known cartons show, there is a need in the fast food industry, particularly those establishments that sell pizzas, for packaging that retains the heat of the hot food without unwanted water condensation forming within the carton, particularly on the underside of the lid.
Developments have been made to allow some of the steam out of such a carton. One such development is the provision of holes or slits on the sides, or near the edges, of the carton. However, for products such as pizzas, the hot air and steam from the center of the pizza cools the steam sufficiently to condense into water on the under surface of the lid above the food before the air and the steam reaches the holes. The holes and slits in the carton are not located directly above the food, which would allow the steam to escape quickly from the carton. The location of holes above the food could permit foreign objects and contaminants to fall on to the food. Furthermore, the use of such direct holes through the panels of the board reduces the strength of the board.